The present invention relates to a thermoplastic elastomer composition. More specifically, the invention relates to a thermoplastic elastomer which can be molded without the need of vulcanization and can exhibit remarkable charateristics with respect to the permanent compression set and oil resistance.
In the field of vulcanized rubbers, increasingly great attention has lately been paid to the so-called thermoplastic elastomers, namely such rubbers which can be molded in a same manner as thermoplastic resins, without the need of vulcanization.
Shortcomings indicated of the known thermoplastic elastomers are that they do not have a satisfactory creap strength, that they cannot compare to vulcanized rubbers with respect to for example the permanent compression set, and also that they are not necessarily satisfactory in respect of the weather resistance.
Then, it is known in the prior art to attain an improvement in or relating to the permanent compression set by adding a gel-containing nitrile rubber to vinyl chloride resins (Japanese patent application Kokai publication No. 61-192754). According to this known method, it is possible to lower the permanent compression set after the lapse of 70 hours at 100.degree. C. to the order of 45%, but it has not yet been possible to attain the same permanent compression set as in the cases of vulcanized rubbers.
Also, with reference to European patent publication No. 194030, this shows a composition comprising a vinylidene fluoride resin and at least one rubber selected from acrylic rubbers, .alpha.,.beta.-unsaturated nitrile-conjugated diene copolymer rubbers (and hydrides of the .alpha.,.beta.-unsaturated nitrile-conjugated diene copolymer rubbers), which composition is described to have a heat resistance and a gasoline resistance which are remarkable and have good tensile strength and elongation. However, to process this composition by molding, it is required to operate a vulcanization step such as for example a press curing using a vulcanizing agent, and the composition cannot be processed in same manners as thermoplastic resins.